The Difference Between Food Allergies, Sensitivities, & Intolerances

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Headaches. Bloating. Phlegm.

Once we recognize the power of healing our gut, we may start to notice symptoms that have been flying under the radar for years… The next question often is, “Do I have a food allergy? Wait, a food sensitivity? Or could it be a food intolerance?”

Well, which is it? You, like me, may have used the terms interchangeably in the past. However, there is a difference, and thankfully, it's not as complicated as it seems!

First, A Word On The Immune System

Our guts contain 70% of our immune system. Therefore, the immune system plays a huge role in this discussion of adverse reactions to food. A properly functioning immune system has two tasks:

To discern the difference between a foreign substance and the body's own healthy tissue;

Although the immune system attacks foreign substances in a variety of ways (see below), one thing remains constant: inflammation.

When a foreign substance invades our bodies, pro-inflammatory chemicals are released. This inflammation halts the spread of pathogens, disposes of the pathogens as the immune system attacks them, and promotes healing. So, you see, inflammation is not inherently a bad thing. Problems arise when the inflammation never fully goes away — which is why it is important to address the underlying cause(s), such as food allergies, sensitivities, and more.

What Are Food Allergies?

Food allergies — also known as immediate hypersensitivity reactions — involve a swift immune response against a food, or food component (usually one or more proteins), that the body thinks is harmful.

When in the presence of this food, certain white blood cells called B lymphocytes produce antibodies. These antibodies attach themselves to the food (a.k.a “invader”) and thereby either mark it for destruction by other parts of the immune system, or neutralize it directly. These antibodies are also known as immunoglobulins, abbreviated Igs.

Most people don't react to an allergen when exposed to it for the first time. Instead, they become “sensitized” to it. This means that the body produces IgE antibodies specific to that allergen, which are primed and ready to attack whenever the allergen is next encountered.

At that point, IgE also triggers the release of a pro-inflammatory chemical called histamine, among others. Histamine spreads through the body, causing the symptoms of an allergic reaction (vomiting, diarrhea, asthma, swelling, hives, even anaphylactic shock) within minutes to hours of exposure. The symptoms can be mild or quite severe, normally affecting the gastrointestinal tract, skin, and/or respiratory system.

How To Diagnose Food Allergies

There are several ways to diagnose food allergies, including blood tests, skin prick tests, and the oral food challenge (the gold standard of food allergy tests). Furthermore, you can keep a food diary and practice an elimination diet.

In the United States, 90% of all food allergies involve the “big eight” food allergens: peanuts, soybeans, fish, crustacea, milk, eggs, tree nuts, and wheat. However, this list changes depending on the country. Sesame seed is a common allergen in Asia and the Middle East, while celery is highly allergenic in Europe. Perhaps dietary patterns do affect the prevalence of certain allergens!

What Are Food Sensitivities?

Food sensitivities — also known as delayed hypersensitivityreactions because they occur within hours to days of exposure — are sometimes categorized as a subset of food allergies. After all, they involve the immune system as well.

What's the difference? Food sensitivities are cell-mediated, not IgE-mediated.

Let's say an individual is sensitive to a few specific foods. When he or she eats these foods, the digestive system breaks them down and they pass into the bloodstream. The immune system recognizes these food particles as foreign, and immunoglobulins such as IgG (sometimes IgM or IgA) activate certain other white blood cells such as T lymphocytes, neutrophils, and macrophages. These white blood cells attack the food particles and release a cascade of pro-inflammatory chemicals, including prostaglandins, interleukins, and even histamine again.

How To Diagnose Food Sensitivities

In addition to elimination diets, the Mediated Release Test (MRT) looks at 130 different foods plus 20 different chemicals and additives to see which ones are causing inflammation, and therefore sensitivity, in individuals.

The IgG test evaluates the presence of food sensitivities as well. However, results aren't entirely accurate or reproducible from lab to lab. Furthermore, antibodies other than IgG may be involved in the sensitivity instead, and so the presence of IgG would be inconsequential (source and source).

What Are Food Intolerances?

Now, we come to food intolerances, which don't involve the immune system at all. These result from an inability to digest a certain food(s). In other words, it's an enzyme issue.

For example, to digest lactose (the disaccharide present in milk), our gut requires the enzyme lactase to break it down into its component parts: two monosaccharides called glucose and galactose. When our digestive systems lack lactase, dairy poses a problem. Lactose can't be absorbed into the bloodstream as-is, and so it passes into the colon, where it is fermented.

This fermentation of the offending food(s) causes general discomfort such as bloating and cramping, but also contributes to the body's toxic load and level of inflammation by releasing pro-inflammatory toxins into the bloodstream (source). Notice that food intolerances cause inflammation as well, despite the fact that the immune system doesn't play a role.

Certain food intolerances known as metabolic food disorders can be passed down genetically from generation to generation.

How To Diagnose Food Intolerances

Also available is the Carroll evaluation, a blood test which checks for an individual's primary food intolerance. Most food intolerances fall into one of these categories: milk, egg, meat, sugar, fruit, and potato. Many individuals also have a combination of foods they don't tolerate well within 4 hours of each other, such as fruit + sugar or grain + potato, so this test checks for secondary pairings as well.

Is It Possible To Heal Food Allergies, Sensitivities, & Intolerances?

It depends…

At the very least, you may be able to put food allergies and sensitivities into remission. The first step is to remove the offending food(s) and then embark on a gut-healing diet such as GAPS. If our bodies are in a constant state of inflammation due to a perpetual barrage of foods they no longer tolerate, healing will not happen. We need to rest, nourish ourselves, and give our guts time to seal properly.

Food intolerances may never go away entirely since they are genetic. It's possible, however, that some individuals may be able to tolerate the foods again in small amounts and occasionally once they are in better health (source).

Interested in healing your gut and putting food allergies and sensitivities into remission? Check out these resources!

About Haniya Cherry

Wardee's oldest daughter, is a Traditional Cooking School child through and through. She enjoys reading biographies and long classic novels, adventuring at the Oregon coast, and learning about the chemistry of food and biology of our bodies. Sourdough, kefir, ginger beer, and apple chutney are her favorite ferments! She and her husband gave birth at home to a baby boy in March 2017. Since then, she can't get enough of anything related to pregnancy, childbirth, and breastfeeding (and she tweets about these topics here)!

Hi Jennifer. Dr. Zeff charges $150 for each food intolerance (Carroll) test. No, a doctor doesn’t need to submit the request. You can simply call his office and request a kit. They send it in the mail within a few business days, then you send the completed kit back (with a $150 check). Once they receive the kit, it doesn’t take them very long to email your results. 🙂 Hope this helps!

Not cheap, but compared to supplements….. In your opinion why don’t more people a) offer the test b) take the test. I found the ED to be extremely difficult for various reasons (some emotional). This seems like an easier way to identify suspect groups. Are the results easily interpreted?

The results are very easily interpreted — Dr. Zeff provides the food you cannot eat plus any foods that react like the original food in the body. It’s a fairly comprehensive list. For example, if you tested intolerant of potato, you wouldn’t be able to eat sweet potatoes, tapioca, arrowroot, etc.

As for why more people don’t take or offer the test, I’m not sure.

There is some controversy surrounding it. Chris Kresser doesn’t think it’s accurate, but his article on the subject isn’t quite accurate either, at least regarding the MRT food sensitivity test. If he’s not 100% accurate about the MRT test, then this of course calls into question his assessment of the Carroll evaluation, too. https://chriskresser.com/are-food-intolerance-tests-accurate/

On the other hand, I know multiple people who have experienced life-changing results by eliminating their food intolerances (see links at the bottom of my post ^^^). My family have all taken it. Some members haven’t noticed any changes, but others have experienced relief from allergies (not food allergies — allergy symptoms like sniffly nose, red eyes, sneezing) and abdominal cramps.

So, in the end, it’s up to you! Feel free to do more research on it. If you’re financially able to take the test, there’s no harm in it and you’ll be able to see if you feel better by taking out the suspect foods. I hope this helps. Sometimes there’s no easy answer to gut issues! 🙂

Thank you for this article explaining the food sensitivities/ intolerances/ allergies. I also had the MRT test done, and then as a Registered Dietitian Nutritionist, I got certified to help people through the process. It was the first time I received any sort of solution for chronic headaches other than just take drugs everyday.

wish I had seen this a few weeks ago. I listened to the Chris Kresser podcast, and even though I wasnt totally confident in the FIT, I took the test, as my doctor recommended it and thinks it has proven accurate in her practice. I would have preferred Cyrex, but $$$$!! So, the FIT says I’m sensitive to eggs. I’ve been egg-free for 10 days now, and don’t feel a bit different. I don’t recall Kresser talking about MRT. How much is it? And is it blood or saliva? Lab visit or mail-in?

Hi Christine! I believe the MRT costs about $500-$600 depending on if you work directly with Oxford BioMedical Technologies (the company which provides the MRT) or through your own practitioner. Practitioners can get the test wholesale so if you go through a doctor, the price really depends on how much (or little) they mark it up.

It’s a blood test and you’d need someone to draw your blood, so either your doctor’s office or an independent lab. If you’re working through your doctor, he or she would ship the blood sample. If you’re doing it independently with Oxford, you’d ship it yourself.

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